1. Field of the Invention
The present invention relates generally to hydraulic nipples used in oil and gas wellbores and, more particularly, to hydraulic nipples adapted to selectively operate as a chemical injection site and/or as a landing site for a wireline retrievable surface control subsurface safety valve.
2. Description of the Related Art
It is often desirable in the oilfield industry to deploy a hydraulic nipple as an integral component of the production tubing at the time of completion or workover. The hydraulic nipple is typically used for the insertion and retrieval of a Wireline Retrievable Surface Controlled Subsurface Safety Valve (“WRSCSSV”) in the event the Tubing Retrievable Surface Controlled Subsurface Safety Valve (“TRSCSSV”) is no longer operable or safety redundancy is needed. A typical hydraulic nipple consists of a lock profile, a single communication port and at least two polished bores which straddle the communication port. The communication port is attached to an external control line, which provides surface control or hydraulic communication to the surface.
There are drawbacks in the traditional nipple design. When the initial completion runs the additional hydraulic nipple, below the safety valve, the control line becomes a leak path around the safety valve. The communication port, having no in line check valve to surface must be isolated off by installing an isolation sleeve, effectively sealing off formation pressure from transmitting around the uphole safety valve and back to the surface. An in-line check valve would render the hydraulic nipple system unacceptable for use as a landing location for a WRSCSSV since releasing the pressure at surface would not allow the valve to close due to trapped pressure between the valve and the check valve.
It is sometimes desirable to inject chemicals downhole for treating the well and/or well systems. In the case of a well which has a TRSCSSV or a WRSCSSV, the hydraulic nipple becomes a good landing location for a chemical injection suspension sleeve and capillary string, since capillary can not be ran from surface through the production pipe, which would render the up-hole safety valve non-functional. In order to accomplish this, costly wellhead modifications are typically necessary since a passageway for the injection string has not previously been provided within the tubing hanger and/or wellhead assembly. This is obviously a time consuming, and thus costly, limitation to the present use of hydraulic nipples. In addition, present day well assemblies generally have a single control line used to operate the TRSCSSV. In the event the control line looses integrity, a complete workover, wherein at least a part of the production tubing is pulled, is required to replace the control line and/or TRSCSSV.
In view of these disadvantages, there is a need in the art for an improved hydraulic nipple and well assembly adapted to selectively facilitate the subsequent injection of chemicals downhole or the insertion of a WRSCSSV without the need to modify the wellhead.